Oil of etherealness was a magical substance that, when applied to a creature, would cause them to cross into the Ethereal Border. The oil appeared a cloudy gray, and the condensation would evaporate quickly from its vial. The oil could cover the creature, the equipment it was wearing, and belongings it was carrying, and generally took around ten minutes to apply.
While the spell was active the caster could move about in the Ethereal plane, but only half as fast if descending or rising. During this time, the creature could see and hear into the original plane that the oil had been applied in. The effects lasted for around an hour, after which the creature would-reappear in its original plane.